Preheat the oven to 425°F. Line a baking sheet with parchment paper.

In a large bowl, whisk together the mashed sweet potatoes and ½ cup milk. Set aside.

In a food processor, combine the flour, cornstarch, sugar, baking powder and salt; pulse to mix. Add the chunks of cold butter and pulse until the mixture resembles coarse meal.

Transfer the flour mixture to the sweet potato mixture. Fold until moistened, adding up to 2 more tablespoons of milk if needed.

Turn the dough onto a floured surface and knead lightly 3 to 4 times. Pat into a rectangle about ¾ inch thick.

Cut the dough into thirds, stack, pat into a rectangle, cut into thirds again, and stack. Pat into a rectangle again with a thickness of about ¾ inch.

Cut into twelve even squares and transfer to the prepared baking sheet. Bake for 13 to 15 minutes until lightly golden.

In a small bowl, beat together the butter, honey, and cinnamon. Serve at room temperature.

The biscuits can be baked and frozen in an airtight container for up to 3 months.